A multi-core microprocessor (or chip-level multiprocessor, CMP) is one that combines two or more independent processors into a single package, often a single integrated circuit (IC). For example, a dual-core device contains two independent microprocessors and a quad-core device contains four microprocessors. A multi-core microprocessor implements multiprocessing in a single physical package. Cores in a multi-core device may share a single coherent cache at the highest on-device cache level or may have separate caches. The processors typically also share the same interconnect to the rest of the system. Each “core” independently implements optimizations such as superscalar execution, pipelining, and multithreading. A system with N cores is effective when it is presented with N or more threads concurrently.
While newer applications are written taking multi-core operations into account and even taking advantage of those, legacy applications designed for single core processor may not operate properly in a multi-core environment. This challenge becomes even more complicated when thread affinity is taken into consideration as well. Thread affinity is where a thread is fixed to run on a particular core.